1. Field of the Invention
The present invention relates to a thin film magnetic head including an inductive head for writing, or a combined thin film magnetic head in which an inductive head for writing and a magnetoresistive (MR) head for reading are laminated. More particularly, the invention relates to a thin film magnetic head in which a coil layer can be properly formed and inductance can be reduced at the same time.
2. Description of the Related Art
FIG. 10 is a longitudinal sectional view of a conventional thin film magnetic head, and the left end of the thin film magnetic head in the drawing corresponds to an air bearing surface (ABS).
This thin film magnetic head is provided on the trailing edge of a slider of a floating-type magnetic head which faces a recording medium such as a hard disk, and is a combined thin film magnetic head including an MR head which uses magnetoresistance for reading and an inductive head for writing.
A lower shielding layer 1 is composed of a magnetic material such as an NiFe alloy (permalloy), and a lower gap layer 2 is formed on the lower shielding layer 1. A magnetoresistive element 3 is formed on the lower gap layer 2. The magnetoresistive element 3 includes a multilayer film 4 composed of a spin-valve element (one type of GMR element) or the like that exhibits magnetoresistance, a pair of hard bias layers (not shown in the drawing) formed on both sides of the multilayer film 4, and an electrode layer (not shown in the drawing) for applying a sensing current to the multilayer film 4.
An upper shielding layer 8 composed of a magnetic material such as an NiFe alloy is further formed on the magnetoresistive element 3 with a nonmagnetic upper gap layer 7 therebetween. As described above, the thin film magnetic head shown in FIG. 10 is a combined thin film magnetic head in which an MR head and an inductive head are laminated, and the upper shielding layer 8 also serves as a lower core layer for the inductive head. Hereinafter, the layer represented by numeral 8 is referred to as a lower core layer.
A gap layer 10 composed of a nonmagnetic material, such as Al2O3 (alumina) or SiO2, is formed on the lower core layer 8. An insulating layer 11 composed of a resist material or other organic materials is further formed on the gap layer 10.
A coil layer 12, composed of a conductive material having low electrical resistance, such as Cu, is spirally formed on the insulating layer 11. The coil layer 12 is formed so as to go around a base 15b of an upper core layer 15, which will be described below.
As shown in FIG. 10, the coil layer 12 is covered by an insulating layer 14 composed of an organic material or the like. A hole is made in the gap layer 10 and the insulating layer 14 formed on the lower core layer 8, and the base 15b of the upper core layer 15 is formed through the hole, thus magnetically coupling the upper core layer 15 and the lower core layer 8.
The upper core layer 15 is formed on the insulating layer 14 in the direction of the ABS (toward the left in the drawing), and a tip 15a of the upper core layer 15 is joined to the lower core layer 8 with the gap layer 10 therebetween at the section facing a recording medium to form a magnetic gap having a gap length Gl.
As shown in FIG. 10, above a coil center 12a of the coil layer 12, which is formed at the rear of the lower core layer 8 (on the right side in the drawing), a hole is made in the insulating layer 14, and a coil lead layer 18 is formed on the coil center 12a through the hole.
For example, the coil lead layer 18 is composed of the same material as that for the upper core layer 15, and is formed simultaneously with the upper core layer 15.
In the inductive head for writing, when a recording current is applied to the coil layer 12, a recording magnetic field is induced in the lower core layer 8 and the upper core layer 15, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer 8 and the tip 15a of the upper core layer 15.
However, in the structure of the thin film magnetic head shown in FIG. 10, a sharp step is produced at the rear of the lower core layer 8 (on the right side in the drawing), and the coil layer 12 must be formed on the insulating layer 11 having the step. If the width of the lower core layer 8 (in the track width direction; perpendicularly with respect to the drawing) is smaller than the width of the coil layer 12, a portion of the coil layer 12 in the width direction must be formed on the insulating layer 11 having the step beneath which the lower core layer 8 is not formed.
That is, in the thin film magnetic head shown in FIG. 10, since the lower core layer 8 is not formed entirely beneath the insulating layer 11 on which the coil layer 12 is to be formed, the coil layer 12 extending beyond the lower core layer 8 must be formed on the insulating layer 11 having the step. When the coil layer 12 is formed on such an insulating layer 11 having the step, it is not possible to pattern the coil layer 12 in a proper shape due to inconsistent focus when a resist layer is exposed during the formation of the coil layer 12.
Additionally, by increasing the pitch of the coil layer 12, patterning of the coil layer 12 can be performed properly to a certain extent. However, if the pitch of the coil layer 12 is increased, the length of the upper core layer 15 form the tip 15a to the base 15b must be increased, and thereby the length of a magnetic path made from the upper core layer 15 through the lower core layer 8 is increased, resulting in an increase in inductance.
FIG. 11 is a partial perspective view of a thin film magnetic head which is improved in order to overcome the problems described above, and FIG. 12 is a longitudinal sectional view of the thin film magnetic head shown in FIG. 11.
As shown in FIG. 11, a lower core layer 16 is formed larger than a coil layer 12. Thus, there is no step in an insulating layer 11 in the region in which the coil layer 12 is to be formed (refer to FIG. 12), and the coil layer 12 can be accurately patterned on a planarized surface (the insulating layer 11).
However, as shown in FIG. 11, if the size of the lower core layer 16 is increased, inductance increases, and in particular, in the coming age of high frequency and high recording density, there is a growing need for a reduction of inductance.
As shown in FIG. 12, the lower core layer 16 has a step 16a, following the steps in the individual layers formed thereunder, and it is not possible to form the coil layer 12 on a completely planarized surface (insulating layer 11). When there is such a step 16a, the pitch of the coil layer 12 must be increased so that the patterning accuracy in the formation of the coil layer 12 is improved, and in accordance with the increase in the pitch of the coil layer 12, the length of an upper core layer 15 must be increased, and thus the length of the magnetic path is increased, resulting in a further increase in inductance.
As described above, in the conventional thin film magnetic heads, the formation of a coil layer on a planarized surface without a step and a reduction in inductance are incompatible.
The present invention has been achieved to overcome the disadvantages associated with the conventional thin film magnetic heads. It is an object of the present invention to provide a thin film magnetic head in which a planarizing layer is formed in the periphery of a lower core layer so that a coil layer is formed properly and inductance is reduced at the same time, and to provide a method of producing the same.
In accordance with the present invention, a thin film magnetic head includes a lower core layer composed of a magnetic material; an upper core layer composed of a magnetic material, a base of the upper core layer being magnetically coupled to the lower core layer, and a tip of the upper core layer facing the lower core layer with a nonmagnetic gap layer therebetween at a section exposed to the air bearing surface; a coil layer, for inducing a recording magnetic field in the lower core layer and the upper core layer, formed so as to go around the base of the upper core layer; and a planarizing layer formed in the periphery of the lower core layer, excluding the section exposed to the air bearing surface, so that the surface of the planarizing layer is level with the surface of the lower core layer, the coil layer being formed on the lower core layer and on the planarizing layer.
Preferably, in accordance with the present invention, the back end of the lower core layer extends to the position in which the base of the upper core layer is magnetically coupled to the lower core layer, and the planarizing layer is formed at the rear of the back end of the lower core layer.
Preferably, in accordance with the present invention, the thin film magnetic head further includes a lower shielding layer, a lower gap layer, a magnetoresistive element including a multilayer film exhibiting magnetoresistance and an electrode layer for applying a sensing current to the multilayer film, and an upper gap layer deposited in that order from the bottom, and the lower core layer is formed thereon, in which the peripheral region, excluding the section exposed to the ABS of each layer from the lower shielding layer to the lower core layer, is filled with the planarizing layer.
Preferably, in accordance with the present invention, the thin film magnetic head further includes a first coil extraction layer simultaneously formed with a main electrode layer, the main electrode layer overlapping the electrode layer constituting the magnetoresistive element and formed at the rear of the electrode layer; and a second coil extraction layer composed of the same material as that for the lower core layer and simultaneously formed with the lower core layer, in which the second coil extraction layer is connected onto the first coil extraction layer, and a coil center of the coil layer is connected onto the second coil extraction layer.
Preferably, in accordance with the present invention, the thin film magnetic head further includes a first coil extraction layer simultaneously formed with a main electrode layer, the main electrode layer overlapping the electrode layer constituting the magnetoresistive element and formed at the rear of the electrode layer; and a third coil extraction layer composed of the same material as that for the lower core layer and simultaneously formed with the lower core layer, in which the third coil extraction layer is connected onto the first coil extraction layer, and a coil lead layer is formed on the third coil extraction layer.
A method of producing a thin film magnetic head in accordance with the present invention includes the steps of: depositing a lower shielding layer, a lower gap layer, a magnetoresistive element, an upper gap layer, and a lower core layer in that order on a substrate; forming a nonmagnetic insulating material layer in the periphery of the lower core layer and over the lower core layer; forming a planarizing layer in the periphery of the lower core layer by removing the surface of the nonmagnetic insulating material layer to expose the lower core layer and by planarizing the exposed surface of the lower core layer and the surface of the nonmagnetic insulating layer in the periphery thereof; forming a gap layer on the lower core layer and on the planarizing layer and further forming a coil layer on the gap layer formed on the lower core layer and on the gap layer formed on the planarizing layer; and forming an insulating layer on the coil layer and further forming an upper core layer composed of a magnetic material on the insulating layer, a base of the upper core layer being magnetically coupled to the lower core layer, a tip of the upper core layer facing the lower core layer with the gap layer therebetween at the section exposed to the air bearing surface.
Preferably, in accordance with the present invention, in the method of producing a thin film magnetic head, the magnetoresistive element is formed by depositing a multilayer film exhibiting magnetoresistance and a pair of electrode layers connected to the multilayer film, and the method further includes the steps of: forming a first coil extraction layer simultaneously with main electrode layers which overlap the electrode layers and extend at the rear of the electrode layers; and connecting a second coil extraction layer and a third coil extraction layer composed of the same material as that for the lower core layer onto the first coil extraction layer. When the coil layer is formed, the coil center is connected onto the second coil extraction layer, and a coil lead layer is further connected onto the third coil extraction layer.
In the conventional thin film magnetic heads, steps are produced in the surfaces for forming coil layers, and thus it is not possible to pattern the coil layers properly. Such steps occur because the coil layers are formed extending beyond the lower core layers formed beneath. Therefore, in order to properly pattern the coil layers, the lower core layers must be formed extending beyond the coil layers so that no step is produced in the surfaces for forming the coil layers.
However, the increased size of the lower core layers results in an increase in inductance, which makes it difficult to adapt to the coming age of high recording density and high frequency.
Therefore, in the present invention, a nonmagnetic layer (hereinafter referred to as a planarizing layer) that is level with a lower core layer is formed in the periphery of the lower core layer and is planarized at the same level as that of the lower core layer so that satisfactory patterning of a coil layer is enabled even if the size of the lower core layer is reduced.
Accordingly, even if the coil layer is formed extending beyond the lower core layer, the coil layer can be formed on a planar surface without a step because the lower core layer and the planarizing layer exist beneath the coil layer.
Furthermore, in accordance with the present invention, because of the formation of the planarizing layer, the lower core layer can be formed in a predetermined shape, and in particular, by reducing the size of the lower core layer, inductance can be decreased.